Author Topic: 3 inch boiler build  (Read 53239 times)

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #120 on: September 18, 2018, 11:59:32 PM »
Thanks both.

@ Peter - yeah, I decided to go for it with the water gauge and get a nice one (which is also regulation compliant). It cost me more than I wanted to spend...  ;)

I will indeed report on the test.


@ Carl - although one of course has to treat boilers with respect, I have learned that there is a sequence of tests which - as long as one follows it - makes any nasty surprises unlikely. If you follow the recognised protocols and use common sense it should be safe enough. I hope.

Yes, the water gauge glass takes the same pressure as everything else in the system. It looks and feels flimsy, but that's what it's designed to do...


Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #121 on: September 19, 2018, 12:01:02 AM »
Cheers Carl, I kinda quite like that little boiler and have thought about buying one. The thing that puts me off is it has quite a lot of tubes and looks a bit of a challenge to someone new to boiler building. I'd like to try something with only a few tubes first  :)

Thing is though Peter - if it doesn't have many tubes you might struggle to run it on coal...   ;)

Offline Gas_mantle

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Re: 3 inch boiler build
« Reply #122 on: September 19, 2018, 12:02:47 AM »

Thing is though Peter - if it doesn't have many tubes you might struggle to run it on coal...   ;)

I was hoping you were going to buy my coal  :Lol:

Offline zeeprogrammer

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Re: 3 inch boiler build
« Reply #123 on: September 19, 2018, 12:58:12 AM »
@Peter...I'm not sure that boiler kit is too much of a challenge. A lot of people have done that model. Marv will also have some insight. Having said that...it's the soldering that concerns me. I don't have much experience and worse...I don't really know what equipment (burner) I need to accomplish it.

@Gary...Quite true regarding respect. It's all in the testing. But boy that water glass is a little concerning.  ;D
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #124 on: September 19, 2018, 06:42:50 AM »

Thing is though Peter - if it doesn't have many tubes you might struggle to run it on coal...   ;)

I was hoping you were going to buy my coal  :Lol:

@Peter - you never know - you might end up using it yourself  :)

@ Carl - from my own limited experience, you are right - the biggest challenge is in the silver soldering, which unfortunately a kit would not preclude. You need a powerful propane torch such as a Seivert or similar - a DIY blowtorch isn't powerful enough.

Will report on the second water test at the weekend. Skimpy as the glass seems to be (like a glass straw really), my main concern at the moment is the top bushing with its thread adaptor 'repair'. I'm hopeful, though, as it passed the first hydro test fitted with a blanking plug...

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #125 on: September 19, 2018, 06:47:14 AM »
I have a boiler kit waiting in the wings. I hesitate to work on it because I know so little about them (and they are bit dangerous).
The water gauge for example is something that I've always wondered about.
The glass is under the same pressure as the boiler, right? Or not?

I don't mean to hijack your thread, Gary. Your thread...like many other members' threads is excellent learning for me.

Carl - no worries - I don't feel hijacked at all  :ThumbsUp:

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #126 on: September 25, 2018, 12:08:43 AM »

The photo below shows a close-up of the water level gauge. Fitting it was easier than I expected, though I won't get too cocky until I have seen it not leaking under pressure.



Ha. So much for that.

The second water pressure test confirmed that the boiler itself is intact and that all fittings are leakproof where they are screwed into the bushes in the boiler.

However, I could not get the water gauge itself to stop leaking where the glass tube meets the fittings. The fittings don't look particularly out of alignment but in my inexperience I have no knowledge of the relevant tolerances. The rubber o-rings are unforgivingly small and skimpy and during my repeated efforts to banish the leaks I shredded them and could find no suitable replacement in my shop.

It gets worse. In my desperation I thought I'd see if putting PTFE tape under the union nuts would do the job. When I was was tightening the bottom union nut I cross-threaded it, ruining the threads. I wish it had been the threads on the nut that I ruined, but it wasn't - it was the threads on the bottom fitting of the very expensive three-cock water gauge. The threaded section looks like it is silver soldered into the fitting and is probably too short to re-thread with a die. This looks to be a costly bit of carelessness on my part as it looks like I'll have to buy a new gauge (or at least the bottom fitting if anyone will sell me one).

But if this is due to a slight misalignment of the fittings, who's to say this won't happen again with new parts?

One thing that may help is this: https://www.glrkennions.co.uk/silicon-tube.html
It looks like it can be used instead of o-rings and it might be a bit more forgiving. I'll give them a ring in the morning.

The annoying thing about this is that with the cocks on the gauge closed off, even without the glass installed, the boiler now sits happily at 1.5 x working pressure until the cows come home. I was hoping to be on to the steam test this week but instead it's more money, more delay and more uncertainty...    :headscratch:

If any of you knowledgeable people have any advice to offer on this I will of course be delighted to hear it...

gary


Offline Gas_mantle

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Re: 3 inch boiler build
« Reply #127 on: September 25, 2018, 12:35:21 AM »
Gary.

Sorry to hear you've hit a snag, but on a positive note the pressure vessel sounds to be fine and the fitting should be a fairly easy fix.

If you are using the 'O' rings that came with the gauge you'd expect them to fit but even so replacements are easy enough to buy. I'm no expert but I'd expect there is just a bit of poor fit/misalignment somewhere. I'd be inclined to just order a few more 'O' rings and give it another try before doing anything else.

I'm not entirely sure where you mean you have stripped the threads, can you explain a bit more?  Assuming you mean you have stripped threads outside of the 'pressure circuit' then it should be fairly easy to fix even if it involves making and soldering a new part.


Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #128 on: September 25, 2018, 12:56:35 AM »
Peter -

Yes, the pressure vessel appears to be sound now and that's the main thing.

I'll certainly order some more o-rings as well of some of that silicone tube and see if I can sort out the gauge. However, I can't do that until the new problem of the damaged threads is resolved.

Look at the photo above. At the bottom end of the glass tube there is a union nut. It's the threads on the actual fitting that the union nut screws on to that are damaged. Part of the 'pressure circuit', unfortunately. The nut will not now go on straight. There isn't enough length in the threaded part to fix with a die and it's probably too knackered anyway. Also, the threaded part appears to be hard soldered into the fitting, and the fitting is very precisely made - probably too precise for me to attempt at this point. It involves two of the valves. I'll have another look at it tomorrow but even if it turns out to be something I could make, I might prefer to bite the bullet and shell out for it rather than get sidetracked into it at this point. One option is I could buy a standard pressure gauge which would be cheaper, but we'll see.

Could have lived without this at this point but there we are...

Offline Gas_mantle

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Re: 3 inch boiler build
« Reply #129 on: September 25, 2018, 01:02:44 AM »
I see what you mean about the union nut now.

While waiting for replacement rings maybe it's worth removing the damaged parts and showing them in close up in the hope someone can suggest a repair?

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #130 on: September 25, 2018, 01:09:29 AM »
Good idea Peter.

Will do that tomorrow...

Offline Jasonb

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Re: 3 inch boiler build
« Reply #131 on: September 25, 2018, 07:15:47 AM »
When fitting the top and bottom halves take the blanking plug out of the top fitting and pass a rod down through it and into the bottom fitting, this should help check that you have them lined up correctly, it wants to be a close fit in them. And will probably have to be turned or a drill bit shank may do.

Just a thought on the sealing, have you got 3/16" tube in a 5mm fitting?

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #132 on: September 25, 2018, 10:34:13 AM »
Thanks Jason.

I was aware of the principle of checking with a rod, but in my hubris I decided that I could just check it with the glass itself. This proved to be an expensive mistake as it indirectly led to the thread on the fitting getting totally buggered up. I have just cut my losses and ordered a new gauge. Plus extra glass and o-rings. Ouch...

I should know better than to ignore established practice which is easily available online.

Next time, the rod (or drill bit)...

It occurs to me that knowing the tolerances in any situation is a big part of this. Even, for example, how much torque a brass blanking plug will stand before it shears. As a beginner I am slowly learning this stuff, sometimes (as in this instance) the hard way.

The glass came with the gauge - both are 5 mm.

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #133 on: September 25, 2018, 10:41:51 AM »
BTW the lady at Blackgates Engineering tells me that it's a good idea to use two o-rings at each end of the glass (i.e. four altogether). She says it makes a better seal.

Offline Tennessee Whiskey

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Re: 3 inch boiler build
« Reply #134 on: September 25, 2018, 01:55:06 PM »
Sounds like a bit of bad luck Gary. Well they say education is expensive no matter how you get it  :facepalm:  Keith Appleton has some really good videos on model boiler fittings and such, if should want to have a look. I feel success for you this time

Whiskey

 

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